PathCAM massive fail on simple model

[Norwegian-Gadgetman]

Hi!

This is probably several separate issues, but I'd do the thorough description in this post then you can possibly create others and link to this as necessary as the errors were all experienced with one model.

The model is a simple mounting bracket for a 'Quiet Cut 30W Spindle'
A picture of the bracket can be seen here:
http://www.shapeoko.com/forum/viewtopic.php?f=5&t=2025&start=110#p37021

To recreate the .stl, use this code in OpenSCAD

difference()
{ union()
{ cube([105, 50, 15]);
translate([55, 45,0])
cylinder(r=45, h=15);
translate([0,45,0])
cube([40, 25, 15]);
translate([105,25,0])
cylinder(r=25, h=15);
}
translate([55, 45,-1])
cylinder(r=26, h=17);
translate([-1, 42, -1])
cube([35, 6, 17]);
translate([35,-1,-1])
cube([40, 6, 17]);
translate([105, 25,-1])
cylinder(r=16, h=17);
translate ([35,4,-1])
cube([5,3.3,17]);
translate ([70,4,-1])
cube([5,3.3,17]);
translate ([40, 17, -1])
cube ([10, 10, 17]);
translate ([60, 17, -1])
cube ([10, 10, 17]);
translate([55, 45, 29])
cylinder(r=15, h=8);

// translate ([120, 25, -1]
// cube ([50,1,17]);
}

First problem is that the smaller hole to the right is treated as a pocket operation.
To 'solve' that, I added the two last lines of the code (remove the // bits to uncomment them) which makes a 1mm wide cut in the wall around the hole, and it gets treated as it should.
(This trick only works if the cut is narrower than the endmill used, though. )

Second problem. I first tried to mill this with a 2mm endmill...
(0.078" )
Unfortunately, the tracks in the 'pocket' (before I found the trick cut) are actually spaced further apart than 2mm.

I went to a 3/16" endmill...
(And the trick cut)
Now, it seems to follow the profile correctly, except...
inside the main hole for the spindle, it follows the edge(finishing cut) first, then does the 'rough cut' later on.

Third problem. There isn't any way to place tabs in the smaller hole to stop the core flopping about and potentially ruin the part. I tried to drag one or two to suitable locations, but it seems they just disappeared. (I edited the G-code manually to solve this)

4th... and this is a biggie...
I specified 8ipm cutting speed and 4ipm Z-speed.
What I got, though, was 25 and 10ipm.
(Thank goodness for search and replace)

Annoyances...
When cutting the smaller hole, and going from rough to finishing cut, it always lift the spindle to the top 'safe' level, even when it just needs to move half a tool diameter to the side.
Then drops down at slow speed.
It's OK to use G0 down to the level that the tool was at on during the previous pass of that cut, then use G1.

The tabs used on the bottom for holding the piece to the material could use 45degree angles instead of 90degree(vertical walls). This will allow for a much smoother cutting operation.

The fact that every G0 and G1 operation has all(X, Y and Z) coordinates defined is a waste of filespace and a potential for slow and jerky cuts on machines that communicate at 9600bps.
(My ShapeOko uses GRBL 0.9c which communicates at 115200)